Removal of lead from aqueous solutions on palm shell activated carbon

The performance of a commercially available palm shell based activated carbon to remove lead ions from aqueous solutions by adsorption was evaluated. The adsorption experiments were carried out at pH 3.0 and 5.0. The effect of malonic and boric acid presence on the adsorption of lead ions was also studied. Palm shell activated carbon showed high adsorption capacity for lead ions, especially at pH 5 with an ultimate uptake of 95.2 mg/g. This high uptake showed palm shell activated carbon as amongst the best adsorbents for lead ions. Boric acid presence did not affect significantly lead uptake, whereas malonic acid decreased it. The diffuse layer surface complexation model was applied to predict the extent of adsorption. The model prediction was found to be in concordance with the experimental values

Electrodeposition of copper and lead on palm shell activated carbon in a flow-through electrolytic cell

Palm shell is an abundant solid waste generated from the palm oil industry in Malaysia. Activated carbon obtained from palm shells has good electrochemical properties and may be used as a working electrode material to remove ions of heavy metals from industrial wastewaters. Results are presented on the electrodeposition of copper and lead ions onto palm shell activated carbon electrodes in terms of current efficiency (). The study was carried out in a continuous packed-bed electrochemical cell. The effects of applied current, solution flow rate, pH of the feed, and presence of complexing agents namely malonic and boric acids on the overall current efficiency were investigated. The results showed that the current efficiency increases with an increase of the flow rate. The application of more negative current to the electrolytic cell resulted in the decrease of current efficiency values. Presence of malonic acid resulted in a relative increase of the current efficiency compared to the single metal system for both pH 3 and 5. The presence of boric acid also resulted in a similar overall increase of the current efficiency. The concentration of the solution leaving the cell strongly depended on the current values applied as well as the solution flow rate; for copper it varied between 0-20 mg/L, and for lead it was between 0-5 mg/L from an inlet value of 50 mg/L for both ions

Study on palm shell activated carbon adsorption capacity to remove copper ions from aqueous solutions

Commercially produced in Malaysia palm shell activated carbon (PSAC) was evaluated in terms of adsorption capacity to remove copper ions from aqueous solutions. The results of batch and continuous adsorption experiments showed high adsorption capacity of the untreated PSAC to adsorb copper ions at pH 3 and 5. Higher pH of aqueous solution showed higher uptake of copper. Presence of complexing agents, boric and malonic acids, did not improve copper uptake. Moreover, lower adsorption capacity was observed in the presence of malonic acid that is probably due to the complex formations between the agent and investigated metal. The observed trends for continuous adsorption of copper are in line with the results obtained for batch mode adsorption. Also, changes of the solutions' initial pHs were measured and they are likely to be associated with the adsorbent's composition and characteristics. In addition, removal of copper ions from the solutions containing lead ions showed that adsorption capacity of copper was not significantly different compared to the single copper ion system. Whereas, the uptake of lead ions onto activated carbon was substantially reduced in the presence of copper ions, especially at pH 5

Continuous adsorption of lead ions in a column packed with palm shell activated carbon

The continuous adsorption of lead ions from aqueous solution on commercial, granular, unpretreated palm shell activated carbon (PSAC) was studied. Effect of pH, flow rates and presence of complexing agents (malonic and boric acids) were examined. The breakthrough period was longer at pH 5 indicating higher adsorption capacity of lead ions at higher pH. Increase of the flow rate, expectedly, resulted in the faster saturation of the carbon bed. Presence of complexing agents did not improve adsorption uptake of lead ions. However, presence of malonic acid resulted in smoother pH stabilization of solution compared to single lead and lead with boric acid systems. The results on continuous adsorption of lead were applied to the model proposed by Wang et al. Y.-H. Wang, S.-H. Lin, R.-S. Juang, Removal of heavy metals ions from aqueous solutions using various low-cost adsorbents, J. Hazard. Mater. B 102 (2003) 291-302. The agreement between experimental and modelled breakthrough curves was satisfactory at both pHs

Fluoride removal by low-cost palm shell activated carbon modified with prawn shell chitosan adsorbents

Hydrofluoric acid is used in large volumes during solar panels manufacturing for cleaning purpose. It results in the generation of wastewater containing high concentrations of fluoride. Chemical precipitation is commonly used to remove most of fluoride from the wastewater. It reduces fluoride concentration to ~ 20 mg/L, whereas the discharge standard is set to 2 mg/L. Adsorption is preferable when dealing with diluted wastewater. This study evaluated the adsorption of fluoride using two low-cost adsorbents: granular palm shell activated carbon and its modification with the prepared chitosan of prawn shells. The effects of pH, dosage, contact time and initial fluoride concentration were studied in batch mode adsorption experiments. The highest removal efficiencies of fluoride by two adsorbents comprised 46% and 55%, respectively, at pH 2 and pH 7. The contrasting behavior of the two adsorbents in relation to pH is attributed by the adsorbents surface charge associated with the surface functional groups identified by FTIR. The adsorption isotherm modeling showed better fit to the Langmuir model for both adsorbents. Adsorption kinetics results fitted well into the pseudo-second-order kinetics model suggesting chemisorption mechanism of fluoride removal

Epitaxial Silver Films Morphology and Optical Properties Evolution over Two Years

Silver and gold are the most commonly used materials in optics and plasmonics. Silver has the lowest optical losses in the visible and near-infrared wavelength range, but it faces a serious problem—degradation over time. It has been repeatedly reported that the optical properties of silver thin films rapidly degrade when exposed to the atmosphere. This phenomenon was described by various mechanisms: rapid silver oxidation, sorption of sulfur or oxygen, formation of silver compounds with chlorine, sulfur, and oxygen. In this work, we systematically studied single-crystalline silver films from 25 to 70 nm thicknesses for almost two years. The surface morphology, crystalline structure and optical characteristics of the silver films were measured using spectroscopic ellipsometry, ultra-high-resolution scanning electron microscopy, and stylus profilometry under standard laboratory conditions. After 19 months, bulk structures appeared on the surface of thin films. These structures are associated with relaxation of internal stresses combined with dewetting. Single-crystalline silver films deposited using the single-crystalline continuous ultra-smooth, low-loss, low-cost (SCULL) technology with a thickness of 35–50 nm demonstrated the best stability in terms of degradation. We have shown that the number of defects (grain boundaries and joints of terraces) is one of the key factors that influence the degradation intensity of silver films